Contact S&W
You can request or download a manual from the S&W website. If that doesn't work for you, find a good gunsmith.
Email or call S&W. You can find in online auctions also.
Go to Smith and Wesson's website and they will send you one for free.
Call S&W and they will tell you.
Compare it to known examples.
Standard Catalog of Smith and Wesoon by Supica and Nahas
Standard Catalog of Smith and Wesson, 3rd ed.
Check the auction sites.
You must call S&W to find out.
You need to find a firearms instructor.
You must call S&W to find out.
Recommend you find a good gunsmith.